Means for protecting operators&#39; ringing leads.



I .PATENTED NOV. 26, 1907.

W. W. DEAN; MEANS FOR PROTECTING QPERATORS RINGING LEADS.

APPLICATION FILED APR. 7, 1906.

ing leads or branches from the power-board but by including a sufficient resistance in the i, generators must be made very much higher than they would otherwise have to be, in ormost desired, because its resistancefalls %TTE% FATET OFFTQE- WILLIAM W. DEAN, OF ELYRIA, OHIO, ASSIGNOR TO THE 'DEAfN ELECTRIC ELYRIA, OHIO, A CORPORATION OF OHIO.

COMPANY. OF

MEANS FOR PROTECTING OPERATORS RINGING; LEADS.

Specification of Letters Patent.

Yatented. Nov. 26,1907.

Application filed April 'hlQOS. Serial No. 310.572-

To all whom it may concern:

Be it known that I, WILLIAM WV. DEAN, a citizen of the United States, residing at Elyria, in the county of Lorain and State of Ohio, have invented certain new and useful Improvements in Means for Protecting Operators Ringing Loads, of which the following is a specification, reference being had therein to the accompanying drawing.

My invention relates to electrical signaling systems, and particularly to the signalin apparatus and circuits-employed in t'lep one exchange systems' It has for its object the provision of means for theprotection of signaling wires or operators rin ing leads from short circuit.

Heretoiore it has been customary'to connect ordinary incandescent lamps in the ringtothe operators keys. Some provision of this kind is necessary, for the reason that the resistance of lines varies widely, and if an would obviously also become short-circuited,

path of the ringing current any injuriousrise thereof due to a short circuit would be prevented.

The objections to the use of incandescent lamps in the manner'stated are as follows? First, the voltage and effective output of the der to overcome the resistance of the lamps when ringing; second: a lamp resistance acts inta mannerdirectly the reverse of what is when hot. Thus, when ringing over a long line of high resistance, the lamp resistance will be at its maximum, thereby cutting down the effective voltage thrown on' the line and when ringing'over a short "line, of low resistance, the lamp heats up and lowers its resistance, thereby raising the effective voltage on the line, and still further, increasin the current.

My invention obviates the disadvantages of the lamp resistances, providing for a normal low resistance, rising to a maximum when the line resistance is below a definite predetermined quantity.

generators,- for talking and signaling respec- Briefiy stated, my invention comprises a high resistance relay with a back contact armature, provided with a low resistance shunt circuit. The relay is so adjusted thatit will not pull up under normal ringing conditions, but when't'he operator rings on a short-circuited line, the consequent large flow of current effectively energizes the relay which pulls up its armature, thereby break ng the low resistance shunt-circuit and causing the current from the generator to traverse the hi h resistance relay windings.

lVIy invention is illustrated in the accompanying drawing, wherein the figure is a diagram showing a subscribers line and substa tion apparatus, with a central oflice connective circuit and ringing key.

In the drawing, A indicates the subscribers station, provided with the usual transmitter, T, receiver, R, switchhook H, and ringer, Q. The line wires 1 and 2 terminate at the central office at the springs j and j of the line jack J which may also have a test thimble When ina condition of disuse, the .jaok springs are closed upon the contact anvils forming terminals of the circuit of the line annunciator, L. For simplicity of illustration I have shown an annunciator of the magneto drop shutter type, but it is. to be understood that my invention is applica-- ble to anytype of system, and that its essential features are unchan ed inianv case, whether the switchboard e a transfer or a multiple board, and its circuits supplied with-- 1 current from a central office batteryfonall purposes or from local batteries and magneto tively.

For interconnecting the linesat the central ofiice cord circuits are provided, each with terminal plugs P and P having the tip and sleeve contacts connected together nespec tively by the conductors 3--5 and 46. For amagneto systemv such as the diagram indi cates, a clearing-out annunciator is bridged across the cord, at L. A suitable listening key is oon11ected in. each cord, but this is omitted from the illustration.

The operators key is shown at K. This has the usual or any desired form of butten or levermanipulated by the operator to move the contact springs Icand k, which between the generator normally rest on contact points formin the terminals of the cord conductors 5 an '6 whereby the tips p and p and the sleeves When the springs.

p and p are joined. Zr and 7c are separated they leave the normal or cord terminals and make contact with the terminals of tlf' generator circuit or ringing lead 7 8, thus'Connecting the generator G through conductors 3 and 4 to the plug P and so to the line 1-2, assuming the plug to have been. inserted in the jack J.

The system thus far described is old and well known, and as I have stated, may be varied in many ways without affecting the essential features of my invention.

In a copending application, Serial No. 27 3,455, filed Au ust 9, 1905, I have shown a low resistance refiay interposed in the path bus and the ringing key, whose windings are connected on the one side to the key contact and on the other to its own armature, or a contact moved thereby. I now discard the relay of the said application and use instead a relay 20 of a out 1,000 ohms resistance interposed between the enerator bus 14 and the path 7 to the key Inshunt with respect to the windings of the relay 20'is a non-inductive resistance 21 of 10 ohms .or thereabout. The branch circuit in which this resistance is placed has its continuity completed through a back contact of the armature 22 of the relay 20. The spring 23 normally holds the armature 22in engagement with its back contact and thereby completes the shunt circuit around the high resistance relay 20.

The relay 20 is so designed that a large current is required to operate it, this being accomplished in a manner well known to al engineers by suitably arranging its magnetic circuit and air gap and adjusting its retractile spring 23. Upon a predetermined rise or leakage of current through it, however, it will operate opening and disconnecting it from the back contact so that the shunt circuit in which the non inductive resistance 21 is placed is broken. This turns the entire force through the relay 20 and that in addition to the drop due to its ohmic resistance, will exercise a.

choking efiect on the current, which in this case, of course, is supposed to be alternating current. When,- however, the ringing current is cut oil, the armature 22 is pulled back to its normal osition by the retractile spring 23, .and the s unt circuit is again completed through the back contact of the armature again introducing the non-inductive resistance 10 which normally remains in the circuit.

by pulling up its armature and The operation is symmetrical and properly rfiirected to produce symmetrical ringing efects.

I do not desire to limit myselfto the construction or arrangement shown and described, as many, chan es might be made in the manner of use and application, particularly as regards the circuits, and all such are contemplated by me. It is equally useful for both direct and-alternating currents.

Having thus described my invention, what I claim and desire to secure by Letters Patent of the United States, is: I 1. In a telephone system, a line circuit, a source of current supply for the line, an inductive resistance between said source and the line, and means including a non-inductive resistance for rendering said inductive resistance normally inoperative.

2. In a telephone system,- a line circuit, a source of signaling current for the line, connection from said source to the line, a high inductive resistance in series in said connection, and a low noninductive resistance in shunt of said high inductive resistance and controlled thereby.

3. In a telephone exchange system, a subscribers station and a central station, and a line circuit interconnecting them, a signal receiving device at the subscribers statlon and a source of signaling current at the central station adapted to be connected to the line;

to ether with a high magnetic resistance be tween said source and the line, and means controlled by said magnet normally com.

pleting a low resistance path from the source to the line. v

4. As a means for protecting operators ringing leads, a high resistance relay therein normally inoperative, and a low resistance shunt around said relay controlled thereby.

5. As a means for protecting operators ringing leads, a relay having high self inductance connected therein and a low noninductive shunt around said relay controlled thereby. I

6. As a means for protectin ope'rators ringing leads, a high resistance re ay connected therein and a low resistance shunt around said relay, said shunt being normally closed through a back contact of said relay whereby when the relay operates, the shunt circuit is rendered inoperatiye.

In testimony whereof I aflix signaturein presence of two witnesses.

WILLIAM 'W. DEAN.

Witnesses:

RAY H. MANsoN, MILLARD E. TAYLOR. 

